Êxodo 29:28

28 This is always to be the perpetual share from the Israelites for Aaron and his sons. It is the contribution the Israelites are to make to the Lord from their fellowship offerings.

28 and it shall be for Aaron and his sons as [their] portion for ever from the children of Israel; for it is a heave-offering: and it shall be a heave-offering from the children of Israel of the sacrifices of their peace-offerings, even their heave-offering unto Jehovah.